Derby Talk

Derby Talk is a forum for Pinewood Derby, Awana Grand Prix, Kub Kar Rally, Shape N Race Derby, Space Derby, Raingutter Regatta and other similar races where a child and an adult work together to create a race vehicle and a lot of fun and memories

Just thought I'd throw this one out there, as I'm sure there must be a simple explanation... When I've been looking at many DIY timers, it seems that the transmitting LED is placed on top, the receiver on the bottom. Isn't that a recipe for interference from the ambient light?

Or is the flash of reflected light from cars finishing a worse situation to have to deal with if the receiver were to be placed on top?